Asymmetrical Anti-rotation Guide Nut for Screw Jacks
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Solution Overview
Problem
Existing anti-rotation mechanisms in cable and screw jacks are bulky, generate significant parasitic vibrations, and are costly due to the use of non-standard parts, which are incompatible with applications requiring fine precision such as exoskeletons and teleoperation.
Innovation Solution
A device for anti-rotation of a driven element around a longitudinal axis using a nut guided by a plane guide that blocks rotation around the longitudinal axis while allowing free rotation around perpendicular axes, with a coupling member connected to the guide nut via a non-concurrent sliding axis, utilizing a splined shaft with recirculating ball bearings for reduced operating clearances and improved precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard machined assemblies (splined shafts) are used for coupling, then translation is allowed while preventing rotation, but the mechanism becomes bulky and requires large clearances that introduce vibrations
Solution Approach 1:
The invention nests the anti-rotation device within the existing guide nut structure. The guide nut (7) with its oblong guide grooves (9) integrates the anti-rotation function directly into the longitudinal guidance mechanism, eliminating the need for separate external anti-rotation assemblies. This nested integration reduces overall mechanism volume while maintaining precision.
Solution Approach 2:
The invention merges the longitudinal guidance function and anti-rotation function into a single integrated guide nut assembly. The oblong guide grooves (9) simultaneously provide longitudinal translation guidance and prevent rotation around the longitudinal axis, combining multiple functions into one compact component rather than requiring separate machined assemblies.
2Volume of moving object
If short smooth shafts are used for coupling, then the mechanism is more compact, but alignment is difficult and significant clearance is required which generates vibrations
Solution Approach 1:
The invention uses an oblong (asymmetric) guide groove cross-section instead of a circular symmetric groove. The oblong shape with perpendicular sides provides inherent alignment features that guide the rollers precisely without requiring difficult alignment of short smooth shafts. The asymmetric geometry naturally constrains the coupling while maintaining compact dimensions.
3Reliability
If non-standard parts are used for the anti-rotation mechanism, then the specific anti-rotation function is achieved, but manufacturing costs increase
Solution Approach 1:
The guide nut (7) with oblong guide grooves (9) performs multiple functions: it provides longitudinal guidance, prevents rotation around the longitudinal axis, and enables compact coupling. By making the guide nut multi-functional rather than requiring specialized non-standard parts, the invention reduces manufacturing costs while achieving the anti-rotation function.
4Device complexity
If the sliding axis between coupling member and guide nut is concurrent with the longitudinal axis, then the structure is simpler, but rotation around perpendicular axes cannot be freely permitted
Solution Approach 1:
The invention offsets the sliding axis from the longitudinal axis, moving it to a different spatial dimension and location. This non-concurrent offset sliding axis configuration allows the coupling member to freely rotate around perpendicular axes while maintaining structural simplicity through the use of standard cylindrical shafts with radial clearance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces vibrations, improves precision, and lowers production costs by using standardized parts, resulting in a more compact and efficient anti-rotation mechanism suitable for applications requiring fine precision.
Implementation Method 1
utilizing a splined shaft with recirculating ball bearings for reduced operating clearances and improved precision
Implementation Method 2
recirculating ball bearings for reduced operating clearances
Data Source
Figure 1
Figure 2~6
AI summary
The invention relates to an anti-rotation device for preventing the rotation of a driven element (4) about a longitudinal axis (Ox), said device comprising: a cross-piece (7) guided in a planar manner on a longitudinal plane parallel to the longitudinal axis of the screw by guiding means (8) that block the rotation of the guiding cross-piece (7) about the longitudinal axis, while allowing the rotation of the guiding cross-piece (7) about two axes perpendicular to the longitudinal axis and perpendicular to one another; and a coupling member (6) at one end of the driven element (4), connected to the guiding cross-piece (7) by linking means that permit a sliding connection (5), the axis (5) of which does not converge with the longitudinal axis. The invention also relates to a screw jack and a cable jack comprising such a device.